Estou a escrever este post para sugerir que quando começarem a fazer o vosso stock de LM congelado o provem ao fim de umas semanas. Isto porque algumas mamãs produzem leite com excesso de lipase (enzima responsável por diminuir a gordura do leite) o que faz com que o leite tenho um cheiro e sabor intensos, pode-se mesmo dizer que sabe a ranço. Não é muito comum, mas pode acontecer. Eu sou uma dessas mamãs.
Vou transcrever a informação que uma conselheira da Mamar ao Peito me enviou:
"A few mothers find that their refrigerated or frozen milk begins to smell or taste soapy, sour, or even rancid soon after it's stored, even though all storage guidelines have been followed closely. Per Lawrence & Lawrence (p. 781), the speculation is that these mothers have an excess of the enzyme lipase in their milk, which begins to break down the milk fat soon after the milk is expressed. Most babies do not mind a mild change in taste, and the milk is not harmful, but the stronger the taste the more likely that baby will reject it.
Lipase is an enzyme that is normally present in human milk and has several known beneficial functions:
Lipases help keep milk fat well-mixed (emulsified) with the "whey" portion of the milk, and also keep the fat globules small so that they are easily digestible (Lawrence & Lawrence, p. 156).
Lipases also help to break down fats in the milk, so that fat soluble nutrients (vitamins A & D, for example) and free fatty acids (which help to protect baby from illness) are easily available to baby (Lawrence & Lawrence, p. 156).
The primary lipase in human milk, bile salt-stimulated lipase (BSSL), "has been found to be the major factor inactivating protozoans" (Lawrence & Lawrence, p. 203).
Per Lawrence & Lawrence (p. 158), the amount of BSSL in a particular mother's milk does not vary during a feed, and is not different at different times of day or different stages of lactation. There is evidence that there may be a decrease in lipase activity over time in mothers who are malnourished.
What can I do if my storage problem is due to excess lipase? Once the milk becomes sour or rancid smelling/tasting, there is no known way to salvage it. However, newly expressed milk can be stored by heating the milk to a scald to inactivate the lipase and stop the process of fat digestion. Scald the milk as soon after expression as possible.
To scald milk:
Heat milk to about 180 F (82 C), or until you see little bubbles around the edge of the pan (not to a full, rolling boil).
Quickly cool and store the milk.
Scalding the milk will destroy some of the antiinfective properties of the milk and may lower some nutrient levels, but this is not likely to be an issue unless all of the milk that baby is receiving has been heat-treated.
Per Lawrence & Lawrence, bile salt-stimulated lipase can also be destroyed by heating the milk at 144.5 F (62.5 C) for one minute (p. 205), or at 163 F (72 C) for up to 15 seconds (p. 771)."
Em Portugês traduzido de Liga La Leche - The Breastfeeding Answer Book):
"Deverá verificar se o seu leite tem tendência a ficar “rançoso”. Isto acontece quando a mãe produz um leite elevado em lipase, a enzima responsável por diminuir a gordura do leite.
O que fazer: Testar, congelando o seu leite, e descongelar passada uma semana. Se cheirar a ranço, deverá passar a escaldar o leite extraído, mas sem o deixar ferver, e depois arrefecê-lo rapidamente e congelá-lo"
Amanhã irei escaldar o leite para ver se resulta. Depois deixo aqui o meu testemunho.
Se resultar, irei falar com a pediatra para saber a opinião dela.